Constructing a 3D multichannel structure to enhance performance of Ni–Co–Mn hydroxide electrodes for flexible supercapacitors

The balancing of the electrochemical performance, mechanical stability, and processing technology for applying supercapacitors to flexible and wearable electronics continues to encounter severe challenges. Herein, we prepare Ni–Co–Mn hydroxide electrodes with a three-dimensional multichannel structure via a simple hydrothermal method. These are constructed using vertically contiguous nanosheets with a uniform thickness and rough surface. The electrodes can provide numerous electroactive sites and accelerate the transmission of electrolyte ions. The relationship between the structure and electrochemical performances is verified by experiments and theoretical calculations. Two-dimensional (2D) planar and one-dimensional (1D) fiber electrodes are prepared using a flexible carbon cloth (CC) and carbon fiber (CF), respectively, as substrates. The assembled quasi-solid-state flexible asymmetric supercapacitor (FASC) with a two-dimensional sandwich structure using NiCoMn–OH/CC as the electrode achieves a remarkable energy density of 73.8 Wh·kg −1 at a power density of 1.03 kW·kg −1 . The quasi-solid–state FASC with a 1D linear structure using NiCoMn–OH/CF as the electrode also attains a high energy density (12.9 Wh·kg −1 at a power density of 0.75 W·kg −1 ). Moreover, the electrochemical performances of the NiCoMn/CC//AC/CC and NiCoMn/CF//AC/CF FASCs are not disturbed at different bending angles (0°, 45°, 90°, 135° and 180°). This indicates the superior flexibility of the devices. We also assemble a self-powered energy-harvesting storage system by integrating FASCs and commercial solar cells to verify its practicability. It displays sustainable development potential for energy storage. Graphical abstract